Extracellular Matrix Stiffness Exists in a Feedback Loop that Drives Tumor Progression

Design approaches for 3D cell culture and 3D bioprinting platforms

The natural habitat of most cells consists of complex and disordered 3D microenvironments with spatiotemporally dynamic material properties. However, prevalent methods of in vitro culture study cells under poorly biomimetic 2D confinement or homogeneous conditions that often neglect critical topographical cues and mechanical stimuli. It has also become increasingly apparent that cells in a 3D conformation exhibit dramatically altered morphological and phenotypical states. In response, efforts toward designing biomaterial platforms for 3D cell culture have taken centerstage over the past few decades. Herein, we present a broad overview of biomaterials for 3D cell culture and 3D bioprinting, spanning both monolithic and granular systems. We first critically evaluate conventional monolithic hydrogel networks, with an emphasis on specific experimental requirements. Building on this, we document the recent emergence of microgel-based 3D growth media as a promising biomaterial platform enabling interrogation of cells within porous and granular scaffolds. We also explore how jammed microgel systems have been leveraged to spatially design and manipulate cellular structures using 3D bioprinting. The advent of these techniques heralds an unprecedented ability to experimentally model complex physiological niches, with important implications for tissue bioengineering and biomedical applications.

Hypoxia effects on glioblastoma progression through YAP/TAZ pathway regulation

The resistance of glioblastomas (GBM) to standard therapies poses a clinical challenge with limited survival despite interventions. The tumor microenvironment (TME) orchestrates GBM progression, comprising stromal and immune cells and is characterized by extensive hypoxic regions. Hypoxia activates the hypoxia-inducible factor 1 alpha (HIF-1α) pathway, interacting with the Hippo pathway (YAP/TAZ) in crucial cellular processes. We discuss here the related signaling crosstalk between YAP/TAZ and regions of hypoxia in the TME with particular attention on the MST1/2 and LATS1/2-regulated YAP/TAZ activation, impacting cell proliferation, invasion, and stemness. Moreover, the hypoxia-YAP/TAZ axis influence on angiogenesis, stem cells, and metabolic regulators is defined. By reviewing extracellular matrix alterations activation of YAP/TAZ, modulation of signaling pathways we also discuss the significance of spatial constraints and epigenetic modifications contribution to GBM progression, with potential therapeutic targets in YAP/TAZ-mediated gene regulation. Comprehensive understanding of the hypoxia-Hippo pathway-TME interplay offers insights for novel therapeutic strategies, aiming to provide new directions for treatment.

Mechanical Properties of Glioblastoma: Perspectives for YAP/TAZ Signaling Pathway and Beyond

Glioblastoma is a highly aggressive brain tumor with a poor prognosis. Recent studies have suggested that mechanobiology, the study of how physical forces influence cellular behavior, plays an important role in glioblastoma progression. Several signaling pathways, molecules, and effectors, such as focal adhesions, stretch-activated ion channels, or membrane tension variations, have been studied in this regard. Also investigated are YAP/TAZ, downstream effectors of the Hippo pathway, which is a key regulator of cell proliferation and differentiation. In glioblastoma, YAP/TAZ have been shown to promote tumor growth and invasion by regulating genes involved in cell adhesion, migration, and extracellular matrix remodeling. YAP/TAZ can be activated by mechanical cues such as cell stiffness, matrix rigidity, and cell shape changes, which are all altered in the tumor microenvironment. Furthermore, YAP/TAZ have been shown to crosstalk with other signaling pathways, such as AKT, mTOR, and WNT, which are dysregulated in glioblastoma. Thus, understanding the role of mechanobiology and YAP/TAZ in glioblastoma progression could provide new insights into the development of novel therapeutic strategies. Targeting YAP/TAZ and mechanotransduction pathways in glioblastoma may offer a promising approach to treating this deadly disease.

Pathophysiology of mesangial expansion in diabetic nephropathy: mesangial structure, glomerular biomechanics, and biochemical signaling and regulation

Diabetic nephropathy, a kidney complication arising from diabetes, is the leading cause of death in diabetic patients. Unabated, the growing epidemic of diabetes is increasing instances of diabetic nephropathy. Although the main causes of diabetic nephropathy have been determined, the mechanisms of their combined effects on cellular and tissue function are not fully established. One of many damages of diabetic nephropathy is the development of fibrosis within the kidneys, termed mesangial expansion. Mesangial expansion is an important structural lesion that is characterized by the aberrant proliferation of mesangial cells and excess production of matrix proteins. Mesangial expansion is involved in the progression of kidney failure in diabetic nephropathy, yet its causes and mechanism of impact on kidney function are not well defined. Here, we review the literature on the causes of mesangial expansion and its impacts on cell and tissue function. We highlight the gaps that still remain and the potential areas where bioengineering studies can bring insight to mesangial expansion in diabetic nephropathy.

Physics of Brain Cancer: Multiscale Alterations of Glioblastoma Cells under Extracellular Matrix Stiffening

The biology and physics underlying glioblastoma is not yet completely understood, resulting in the limited efficacy of current clinical therapy. Recent studies have indicated the importance of mechanical stress on the development and malignancy of cancer. Various types of mechanical stress activate adaptive tumor cell responses that include alterations in the extracellular matrix (ECM) which have an impact on tumor malignancy. In this review, we describe and discuss the current knowledge of the effects of ECM alterations and mechanical stress on GBM aggressiveness. Gradual changes in the brain ECM have been connected to the biological and physical alterations of GBM cells. For example, increased expression of several ECM components such as glycosaminoglycans (GAGs), hyaluronic acid (HA), proteoglycans and fibrous proteins result in stiffening of the brain ECM, which alters inter- and intracellular signaling activity. Several mechanosensing signaling pathways have been identified that orchestrate adaptive responses, such as Hippo/YAP, CD44, and actin skeleton signaling, which remodel the cytoskeleton and affect cellular properties such as cell–cell/ECM interactions, growth, and migration/invasion of GBM cells. In vitro, hydrogels are used as a model to mimic the stiffening of the brain ECM and reconstruct its mechanics, which we also discuss. Overall, we provide an overview of the tumor microenvironmental landscape of GBM with a focus on ECM stiffening and its associated adaptive cellular signaling pathways and their possible therapeutic exploitation.

Mechanisms of Pharmacoresistance in Hepatocellular Carcinoma: New Drugs but Old Problems

Hepatocellular carcinoma (HCC) is a malignancy with poor prognosis when diagnosed at advanced stages in which curative treatments are no longer applicable. A small group of these patients may still benefit from transarterial chemoembolization. The only therapeutic option for most patients with advanced HCC is systemic pharmacological treatments based on tyrosine kinase inhibitors (TKIs) and immunotherapy. Available drugs only slightly increase survival, as tumor cells possess additive and synergistic mechanisms of pharmacoresistance (MPRs) prior to or enhanced during treatment. Understanding the molecular basis of MPRs is crucial to elucidate the genetic signature underlying HCC resistome. This will permit the selection of biomarkers to predict drug treatment response and identify tumor weaknesses in a personalized and dynamic way. In this article, we have reviewed the role of MPRs in current first-line drugs and the combinations of immunotherapeutic agents with novel TKIs being tested in the treatment of advanced HCC.

Cancer-associated fibroblasts promote oral squamous cell carcinoma progression through LOX-mediated matrix stiffness

Background

Cancer-associated fibroblasts (CAFs), the most abundant cells in the tumor microenvironment, have prominent roles in the development of solid tumors as stromal targets. However, the underlying mechanism of CAFs’ function in oral squamous cell carcinoma (OSCC) development remains unclear. Here, we investigated the role of lysyl oxidase (LOX) expression in CAFs in tumor stromal remodeling and the mechanism of its effect on OSCC progression.

Methods

Multiple immunohistochemistry (IHC) staining was performed to detect the correlation of CAFs and LOX in the stroma of OSCC specimens, as well as the correlation with clinicopathological parameters and prognosis. The expression of LOX in CAFs were detected by RT-qPCR and western blot. The effects of LOX in CAFs on the biological characteristics of OSCC cell line were investigated using CCK-8, wound-healing and transwell assay. CAFs were co-cultured with type I collagen in vitro, and collagen contraction test, microstructure observation and rheometer were used to detect the effect of CAFs on remodeling collagen matrix. Then, collagen with different stiffness were established to investigate the effect of matrix stiffness on the progression of OSCC. Moreover, we used focal adhesion kinase (FAK) phosphorylation inhibitors to explored whether the increase in matrix stiffness promote the progression of OSCC through activating FAK phosphorylation pathway.

Results

LOX was colocalized with CAFs in the stroma of OSCC tissues, and its expression was significantly related to the degree of malignant differentiation and poor prognosis in OSCC. LOX was highly expressed in CAFs, and its knockdown impaired the proliferation, migration, invasion and EMT process of OSCC cells. The expression of LOX in CAFs can catalyze collagen crosslinking and increase matrix stiffness. Furthermore, CAFs-derived LOX-mediated increase in collagen stiffness induced morphological changes and promoted invasion and EMT process in OSCC cells by activating FAK phosphorylation pathway.

Conclusions

Our findings suggest that CAFs highly express LOX in the stroma of OSCC and can remodel the matrix collagen microenvironment, and the increase in matrix stiffness mediated by CAFs-derived LOX promotes OSCC development through FAK phosphorylation pathway. Thus, LOX may be a potential target for the early diagnosis and therapeutic treatment of OSCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03181-x.

Myeloperoxidase: Growing importance in cancer pathogenesis and potential drug target

Myeloperoxidase is a heme-peroxidase which makes up approximately 5% of the total dry cell weight of neutrophils where it is predominantly found in the primary (azurophilic) granules. Other cell types, such as monocytes and certain macrophage subpopulations also contain myeloperoxidase, but to a much lesser extent. Initially, the function of myeloperoxidase had been mainly associated with its ability as a catalyzer of reactive oxidants that help to clear pathogens. However, over the past years non-canonical functions of myeloperoxidase have been described both in health and disease. Attention has been specially focused on inflammatory diseases, in which an exacerbate infiltration of leukocytes can favor a poorly-controlled production and release of myeloperoxidase and its oxidants. There is compelling evidence that myeloperoxidase derived oxidants contribute to tissue damage and the development and propagation of acute and chronic vascular inflammation. Recently, neutrophils have attracted much attention within the large diversity of innate immune cells that are part of the tumor microenvironment. In particular, neutrophil-derived myeloperoxidase may play an important role in cancer development and progression. This review article aims to provide a comprehensive overview of the roles of myeloperoxidase in the development and progression of cancer. We propose future research approaches and explore prospects of inhibiting myeloperoxidase as a strategy to fight against cancer.

Inhibition of matrix stiffness relating integrin β1 signaling pathway inhibits tumor growth in vitro and in hepatocellular cancer xenografts

Background

Cancer development is strictly correlated to composition and physical properties of the extracellular matrix. Particularly, a higher matrix stiffness has been demonstrated to promote tumor sustained growth. Our purpose was to explore the role of matrix stiffness in liver cancer development.

Methods

The matrix stiffness of tumor tissues was determined by atomic force microscopy (AFM) analysis. In vitro, we used a tunable Polyacrylamide (PA) hydrogels culture system for liver cancer cells culture. The expression level of integrin β1, phosphorylated FAK, ERK1/2, and NF-κB in SMMC-7721 cells was measured by western blotting analysis. We performed MTT, colony formation and transwell assay to examine the tumorigenic and metastatic potential of SMMC-7721 cells cultured on the tunable PA hydrogels. SMMC-7721 cancer xenografts were established to explore the anticancer effects of integrin inhibitors.

Results

Our study provided evidence that liver tumor tissues from metastatic patients possessed a higher matrix stiffness, when compared to the non-metastatic group. Liver cancer cells cultured on high stiffness PA hydrogels displayed enhanced tumorigenic potential and migrative properties. Mechanistically, activation of integrin β1/FAK/ ERK1/2/NF-κB signaling pathway was observed in SMMC-7721 cells cultured on high stiffness PA hydrogels. Inhibition of ERK1/2, FAK, and NF-κB signaling suppressed the pro-tumor effects induced by matrix stiffness. Combination of chemotherapy and integrin β1 inhibitor suppressed the tumor growth and prolonged survival time in hepatocellular cancer xenografts.

Conclusion

A higher matrix stiffness equipped tumor cells with enhanced stemness and proliferative characteristics, which was dependent on the activation of integrin β1/FAK/ERK1/2/NF-κB signaling pathway. Blockade of integrin signals efficiently improved the outcome of chemotherapy, which described an innovative approach for liver cancer treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08982-3.

Intra-Tumour Genetic Heterogeneity and Prognosis in High-Risk Neuroblastoma

Spatial ITH is defined by genomic and biological variations within a tumour acquired by tumour cell evolution under diverse microenvironments, and its role in NB patient prognosis is understudied. In this work, we applied pangenomic techniques to detect chromosomal aberrations in at least two different areas of each tumour and/or in simultaneously obtained solid and liquid biopsies, detecting ITH in the genomic profile of almost 40% of HR-NB. ITH was better detected when comparing one or more tumour pieces and liquid biopsy (50%) than between different tumour pieces (21%). Interestingly, we found that patients with ITH analysed by pangenomic techniques had a significantly better survival rate that those with non-heterogeneous tumours, especially in cases without MYCN amplification. Moreover, all patients in the studied cohort with high ITH (defined as 50% or more genomic aberration differences between areas of a tumour or simultaneously obtained samples) survived after 48 months. These results clearly support analysing at least two solid tumour areas (separately or mixed) and liquid samples to provide more accurate genomic diagnosis, prognosis and therapy options in HR-NB.

Characterizing the Invasive Tumor Front of Aggressive Uterine Adenocarcinoma and Leiomyosarcoma

The invasive tumor front (the tumor–host interface) is vitally important in malignant cell progression and metastasis. Tumor cell interactions with resident and infiltrating host cells and with the surrounding extracellular matrix and secreted factors ultimately determine the fate of the tumor. Herein we focus on the invasive tumor front, making an in-depth characterization of reticular fiber scaffolding, infiltrating immune cells, gene expression, and epigenetic profiles of classified aggressive primary uterine adenocarcinomas (24 patients) and leiomyosarcomas (11 patients). Sections of formalin-fixed samples before and after microdissection were scanned and studied. Reticular fiber architecture and immune cell infiltration were analyzed by automatized algorithms in colocalized regions of interest. Despite morphometric resemblance between reticular fibers and high presence of macrophages, we found some variance in other immune cell populations and distinctive gene expression and cell adhesion-related methylation signatures. Although no evident overall differences in immune response were detected at the gene expression and methylation level, impaired antimicrobial humoral response might be involved in uterine leiomyosarcoma spread. Similarities found at the invasive tumor front of uterine adenocarcinomas and leiomyosarcomas could facilitate the use of common biomarkers and therapies. Furthermore, molecular and architectural characterization of the invasive front of uterine malignancies may provide additional prognostic information beyond established prognostic factors.

Impact of extracellular matrix stiffness on genomic heterogeneity in MYCN-amplified neuroblastoma cell line

BACKGROUND

Increased tissue stiffness is a common feature of malignant solid tumors, often associated with metastasis and poor patient outcomes. Vitronectin, as an extracellular matrix anchorage glycoprotein related to a stiff matrix, is present in a particularly increased quantity and specific distribution in high-risk neuroblastoma. Furthermore, as cells can sense and transform the proprieties of the extracellular matrix into chemical signals through mechanotransduction, genotypic changes related to stiffness are possible.

METHODS

We applied high density SNPa and NGS techniques to in vivo and in vitro models (orthotropic xenograft vitronectin knock-out mice and 3D bioprinted hydrogels with different stiffness) using two representative neuroblastoma cell lines (the MYCN-amplified SK-N-BE(2) and the ALK-mutated SH-SY5Y), to discern how tumor genomics patterns and clonal heterogeneity of the two cell lines are affected.

RESULTS

We describe a remarkable subclonal selection of genomic aberrations in SK-N-BE(2) cells grown in knock-out vitronectin xenograft mice that also emerged when cultured for long times in stiff hydrogels. In particular, we detected an enlarged subclonal cell population with chromosome 9 aberrations in both models. Similar abnormalities were found in human high-risk neuroblastoma with MYCN amplification. The genomics of the SH-SY5Y cell line remained stable when cultured in both models.

CONCLUSIONS

Focus on heterogeneous intratumor segmental chromosome aberrations and mutations, as a mirror image of tumor microenvironment, is a vital area of future research.

Physicochemical Tools for Visualizing and Quantifying Cell-Generated Forces

To discern how mechanical forces coordinate biological outcomes, methods that map cell-generated forces in a spatiotemporal manner, and at cellular length scales, are critical. In their native environment, whether it be within compact multicellular three-dimensional structures or sparsely populated fibrillar networks of the extracellular matrix, cells are constantly exposed to a slew of physical forces acting on them from all directions. At the same time, cells exert highly localized forces of their own on their surroundings and on neighboring cells. Together, the generation and transmission of these forces can control diverse cellular activities and behavior as well as influence cell fate decisions. To thoroughly understand these processes, we must first be able to characterize and measure such forces. However, our experimental needs and technical capabilities are in discord-while it is apparent that we should study cell-generated forces within more biologically relevant 3D environments, this goal remains challenging because of caveats associated with complex "sensing-transduction-readout" modalities. In this Review, we will discuss the latest techniques for measuring cell-generated forces. We will highlight recent advances in traction force microscopy and examine new alternative approaches for quantifying cell-generated forces, both of individual cells and within 3D tissues. Finally, we will explore the future direction of novel cellular force-sensing tools in the context of mechanobiology and next-generation biomaterials design.

Circulating tumour cells in head and neck cancers: Biological insights

Tumour metastasis is one of the leading cause of cancer-related mortality. Circulating tumour cells (CTCs) have been implicated in loco-regional and distant metastasis and its role is being extensively studied in various malignancies, including those from the head and neck region. The main challenge in understanding their significance lies in the rarity of these cells in the blood. However, newer technologies have attempted to overcome these pitfalls. This review explores the evolution of CTC research and other related areas, including its biological significance, sustainability within the circulating vascular environment and possible clinical implications.

Human Organ-Specific 3D Cancer Models Produced by the Stromal Self-Assembly Method of Tissue Engineering for the Study of Solid Tumors

Cancer research has considerably progressed with the improvement of in vitro study models, helping to understand the key role of the tumor microenvironment in cancer development and progression. Over the last few years, complex 3D human cell culture systems have gained much popularity over in vivo models, as they accurately mimic the tumor microenvironment and allow high-throughput drug screening. Of particular interest, in vitrohuman 3D tissue constructs, produced by the self-assembly method of tissue engineering, have been successfully used to model the tumor microenvironment and now represent a very promising approach to further develop diverse cancer models. In this review, we describe the importance of the tumor microenvironment and present the existing in vitro cancer models generated through the self-assembly method of tissue engineering. Lastly, we highlight the relevance of this approach to mimic various and complex tumors, including basal cell carcinoma, cutaneous neurofibroma, skin melanoma, bladder cancer, and uveal melanoma.

Changes in extracellular matrix in different stages of colorectal cancer and their effects on proliferation of cancer cells

BACKGROUND

The extracellular matrix is the main component of the tumor microenvironment. Extracellular matrix remodels with the oncogenesis and development of tumors. Previous studies usually focused on the changes of proteins in normal colorectal tissues and colorectal cancers. Little is known about the changes in the extracellular matrix in different stages of colorectal cancer and the effects of these changes on the development of this cancer.

AIM

To test the changes of type I collagen, type IV collagen, matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9), and tissue inhibitor of metalloproteinase-3 (TIMP-3) in different stages of colorectal cancer and the effects of these changes on the proliferation of cancer cells.

METHODS

The extracellular matrix from various stages of colorectal cancer and normal colon tissue was obtained by using acellular technology. We used proteomics to detect the differential expression of proteins between normal colon tissues and colorectal cancer tissues, and then we used Western blot to observe their expression in each stage of colorectal cancer and in normal colon tissue. By co-culturing the extracellular matrix and HT29 colon cancer cells in vivo and in vitro, we tested the cancer cell proliferation rate in vitro by methyl thiazolyl tetrazolium (MTT) assay and in vivo by measuring the tumor volume.

RESULTS

The expression of type I collagen and MMP-2 increased with increased tumor stage. The expression of MMP-9 was higher in colorectal cancer tissues and was highest in stage III cancer. The expression of type IV collagen and TIMP-3 decreased with increased tumor stage. The proliferation rate of cancer cells in the extracellular matrix of colorectal cancer was higher than that in the extracellular matrix of the normal colon.

CONCLUSION

These data suggest that the extracellular matrix structure and composition become disorganized during the development of tumors, which is more conducive for the growth of cancer cells.

An Interplay Between Reaction-Diffusion and Cell-Matrix Adhesion Regulates Multiscale Invasion in Early Breast Carcinomatosis

The progression of cancer in the breast involves multiple reciprocal interactions between malignantly transformed epithelia, surrounding untransformed but affected stromal cells, and the extracellular matrix (ECM) that is remodeled during the process. A quantitative understanding of the relative contribution of such interactions to phenotypes associated with cancer cells can be arrived at through the construction of increasingly complex experimental and computational models. Herein, we introduce a multiscale three-dimensional (3D) organo- and pathotypic experimental assay that approximates, to an unprecedented extent, the histopathological complexity of a tumor disseminating into its surrounding stromal milieu via both bulk and solitary motility dynamics. End point and time-lapse microscopic observations of this assay allow us to study the earliest steps of cancer invasion as well as the dynamical interactions between the epithelial and stromal compartments. We then simulate our experimental observations using the modeling environment Compucell3D that is based on the Glazier-Graner-Hogeweg model. The computational model, which comprises adhesion between cancer cells and the matrices, cell proliferation and apoptosis, and matrix remodeling through reaction-diffusion-based morphogen dynamics, is first trained to phenocopy controls run with the experimental model, wherein one or the other matrices have been removed. The trained computational model successfully predicts phenotypes of the experimental counterparts that are subjected to pharmacological treatments (inhibition of N-linked glycosylation and matrix metalloproteinase activity) and scaffold modulation (alteration of collagen density). Further parametric exploration-based simulations suggest that specific permissive regimes of cell-cell and cell-matrix adhesions, operating in the context of a reaction-diffusion-regulated ECM dynamics, promote multiscale invasion of breast cancer cells and determine the extent to which the latter migrate through their surrounding stroma.

Immune Conversion of Tumor Microenvironment by Oncolytic Viruses: The Protoparvovirus H-1PV Case Study

Cancer cells utilize multiple mechanisms to evade and suppress anticancer immune responses creating a “cold” immunosuppressive tumor microenvironment. Oncolytic virotherapy is emerging as a promising approach to revert tumor immunosuppression and enhance the efficacy of other forms of immunotherapy. Growing evidence indicates that oncolytic viruses (OVs) act in a multimodal fashion, inducing immunogenic cell death and thereby eliciting robust anticancer immune responses. In this review, we summarize information about OV-mediated immune conversion of the tumor microenvironment. As a case study we focus on the rodent protoparvovirus H-1PV and its dual role as an oncolytic and immune modulatory agent. Potential strategies to improve H-1PV anticancer efficacy are also discussed.

Crosstalk between tumor cells and lymphocytes modulates heparanase expression

Background

Heparanase (HPSE) is an endo-beta-glucuronidase that degrades heparan sulfate (HS) chains on proteoglycans. The oligosaccharides generated by HPSE promote angiogenesis, tumor growth and metastasis. Heparanase-2 (HPSE2), a close homolog of HPSE, does not exhibit catalytic activity. Previous studies have demonstrated that serum or plasma from breast cancer patients showed increased expression of both heparanases in circulating lymphocytes. The aim of this study was to better understand the mechanisms involved in the upregulation of heparanases in circulating lymphocytes.

Methods

Lymphocytes collected from healthy women were incubated in the presence of MCF-7 breast cancer cells (co-culture) to stimulate HPSE and HPSE2 overexpression. The protein level of heparanases was evaluated by immunocytochemistry, while mRNA expression was determined by quantitative RT-PCR.

Results

The medium obtained from co-culture of MCF-7 cells and circulating lymphocytes stimulated the expression of HPSE and HPSE2. Previous treatment of the co-culture medium with an anti-heparan sulfate proteoglycan antibody or heparitinase II inhibited the upregulation of heparanases in circulating lymphocytes. The addition of exogenous heparan sulfate (HS) enhanced the expression of both heparanases. Moreover, the co-cultured cells, as well as MCF-7 cells, secreted a higher number of exosomes expressing an increased level of HS compared to that of the exosomes secreted by circulating lymphocytes from women who were not affected by cancer.

Conclusions

The results revealed that HS is likely responsible for mediating the expression of heparanases in circulating lymphocytes. HS secreted by tumor cells might be carried by exosome particles, confirming the key role of tumor cells, as well as secreted HS, in upregulating the expression of heparanases, suggesting a possible mechanism of crosstalk between tumor cells and circulating lymphocytes.